Nolan: As far as me sticking by your side, I think you know by now I'm not going anywhere.Emily: Then don't ever tell me to let go, or to ease up, or to forgive. Not when I'm standing here covered in the blood of one of the only people that I ever loved.

In its purest form, an act of retribution provides symmetry, the rendering of payment for crimes against the innocent. but the danger of retaliation lies in furthering the cycle of violence. Still, it's a risk that must be met when the greater offense is to allow the guilty to go unpunished.